Method and apparatus for physiological testing

ABSTRACT

A device and method to test the sincerity of physical effort of an individual. The device has a moveable member, a sensor for measuring force applied to the shaft; and a resistance means to vary the resistance to movement of the moveable member. The relationship between the varied resistive force applied to the moveable member and the measured force may be determined to establish the sincerity of effort of the user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation in part of International patent application NoPCT/AU2004/001038 published as WO 2005/013821, the entire contents ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for measuring theperformance of human joints.

BACKGROUND OF THE INVENTION

The present invention is concerned with measuring the performance of ajoint or combination of such in the human body and, in particular, tomeasuring the effort exerted by a patient during the performance testingprocess.

When persons suffer injuries in accidents such as those which commonlyoccur in the workplace, and in road traffic accidents, it is usuallynecessary for the extent of the injured person's injuries to bedetermined in order to assess the correct amount of compensation whichmay be payable to the injured person as a result of the accident.Typically the compensation payable will be related to the extent of theperson's injuries and the loss of use or performance of parts of theperson's body due to the accident. For example, if a person injurestheir arm in an accident the compensation payable will depend on theextent to which that person's use of their arm has been impaired.Further, an accurate assessment of an injury allows a rehabilitationprogramme to be monitored and varied if necessary.

However, there is currently no satisfactory repeatable scientific methodof assessing a person's joint performance to determine to what extentthe performance of the joint has been impaired due to injury or accidentor the like. Currently, most injuries are assessed subjectively bydoctors or physiotherapists. The assessment process is generallyunscientific and open to inaccuracies. One particular problem occurswhen patients pretend to be more seriously injured than they are forexample by pretending to be unable to do particular tasks or by onlyproviding a sub-maximal effort when tested.

This is a major problem for organisations which provide insurancepayments related to injuries, particularly insurance companies.

A further related problem arises, in that since it is not possible toaccurately measure joint performance, it is not possible to accuratelymeasure improvement in joint performance. Thus if a patient isundergoing physiotherapy or other treatment for injuries associated witha joint it is not, for example, possible to accurately plot improvementor lack of fit in the joint on a week by week basis.

The present invention aims to provide a device for repeatedly andaccurately measuring the performance of a joint in the body and whichpreferably includes means for determining whether the patient whosejoint performance is being measured is making a minimal or at leastsub-maximal effort, when tested.

Throughout this specification the word “comprise”, or variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated element, integer or step, or group of elements, integers orsteps, but not the exclusion of any other element, integer or step, orgroup of elements, integers or steps.

Any discussion of documents, acts, materials, devices, articles or thelike which has been included in the present specification is solely forthe purpose of providing a context for the present invention. It is notto be taken as an admission that any or all of these matters form partof the prior art base or were common general knowledge in the fieldrelevant to the present invention as it existed before the priority dateof each claim of this application.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a device for performancetesting of a human's joints comprising:

a moveable member;

a sensor for measuring force applied to the moveable member by thehuman; and

a resistance means for varying the resistance to movement of themoveable member at least once during a single movement of the moveablemember by the human; and

means for comparing, or determining the correlation between, themeasured force applied to the movable member with the resistance tomovement of the movable member for assessing the response of the humanto the variation in resistance to provide an indication of the human'ssincerity of effort in moving the movable member.

The moveable member may be a shaft or a lever.

Alternatively, the movable member may be a piston in a hydrauliccylinder.

Many other types of movable member may be possible, such a brakessliding on a bar or shaft.

Mechanisms, such as chains or belt and sprocket drives, may be connectedto the movable member to convert rotational or linear movement of themember to other types of movement. For example, a cable/capstan andangle sensing device could be used for handling linear/compoundmovement.

Where the moveable member is a shaft, the shaft may be rotatable. Inthis embodiment, the sensor may comprise a torque sensor for measuringtorque applied to the shaft.

Where the movable member is a piston of a hydraulic cylinder, the sensormay comprise a pressure sensor measuring the fluid pressure inside thecylinder. An adjustable control valve, controlling the exit of fluidfrom the cylinder.

Two or more cylinders acting together could be used.

The resistance means may comprise a coupling means that variably couplesthe shaft to the torque sensor. Such variable coupling of shaft andtorque sensor varies the resistance to the turning of the shaft. Anexample of such a resistance means is an electric brake, eddy coupling,servo motor or the like.

Where the resistance means comprises a coupling means, typically theresistance is variable between a state where there is no coupling and noresistance is applied and the shaft is free to rotate relative to thetorque sensor and a state in which the shaft is fully coupled to thetorque sensor.

It is preferred that the device includes an encoder for measuring theposition of the shaft. The device may also include a control means forreceiving input data from the torque sensor. The control means may alsobe arranged to input control signals to the resistance means and todetermine the relationship between the resistance applied to the shaftand the torque measured by the torque sensor. Further, the control meansmay receive signals from the encoder in relation to the angular positionof the shaft.

Where the moveable member comprises a lever, said lever may be connectedto a resistance means. The resistance means may comprise a pump member.The pump member typically has a control valve to vary resistance to thelever. Further, the pump member of this embodiment may be connected to asensor, said sensor measuring the force applied to the lever. The sensormay comprise a pressure gauge to measure the pressure change of fluid inthe pump as force is applied to the lever.

A number of devices may be operated together simultaneously to deal withmovement in multiple axes.

In one broad related aspect, the present invention provides a method ofsincerity of effort testing of a person's joint performance byrepeatedly measuring the response of that joint to a varying load.

More specifically, the present invention provides a method of measuringa person's joint performance and simultaneously measuring sincerity ofeffort by

getting the person to apply force to a movable member to move thatmember;

varying the resistance to movement of the member at least once during asingle movement;

measuring the force applied to the member by the person,

recording the resistive force applied; and

assessing the correlation between the resistive force applied and themeasured torque to thereby assess the sincerity of effort applied by theperson to movement of the member.

In a related aspect, the invention provides a method of sincerity ofeffort testing of a person's joint performance by measuring the torqueapplied to a shaft by one of the person's joints comprising the stepsof:

applying a varying resistive force to turning of the shaft, theresistance to turning of the shaft being varied at least once during asingle movement;

measuring the torque applied to the shaft;

recording the resistive force applied; and

assessing the correlation between the resistive force applied and themeasured torque to provide an indication of the sincerity of effortapplied by the person to movement of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

A specific example of the present invention will now be described by wayof example only and with reference to the accompanying drawings inwhich:

FIG. 1 is a schematic drawing of a device for repeated performancemeasuring to gauge sincerity of effort;

FIGS. 2 and 3 are graphs comparing the resistive load applied to thedevice against measured torque; and

FIG. 4 is a schematic drawing of a second embodiment of a device fortesting sincerity of effort.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, in particular FIG. 1, the device generallyindicated at 10, includes a rectangular box-like casing 12. One side ofa torque sensor 14 is mounted to one interior wall 15 of the casing.Fixed to the opposite side of the torque sensor 14 is a mounting plate16 defining a central hole 18 through which one end of an elongate shaft20 extends. The end of the shaft 20 is free to rotate relative to themounting plate and the torque sensor 14. The shaft 20 extends from themounting plate 16 co-axial with the torque sensor 14 and defines a freeend 21 which projects through an aperture 22 defined in a wall 24 of thecasing opposite to the wall 15 to which the torque sensor 14 is mounted.

The free end 21 of the shaft 20 defines a coupling 26 which can beattached to various joint testing interfaces for testing any joints orcombinations of such which can be used to produce rotary motion about anaxis, which most if not all joints are capable of.

A brake stator coil 28 defining a central bore 30 which is of greaterdiameter than the shaft is fixed to the mounting plate 16. The shaft 20extends through that central bore 30. A brake rotor 32 is mounted on theshaft 20 and defines a friction surface 34 facing the brake stator coil28 and in conjunction with the brake stator coil 28 defines an electricbrake. Increasing the current supplied to the brake rotor 32 increasesthe resistance between the brake rotor 32 and the brake stator coil 28and hence the coupling between the two. When the current is a maximumand the brake is fully on any torque applied to the shaft 20 istransmitted directly to the torque sensor 14. When the brake is fullydisengaged, the shaft 20 spins freely and no torque is applied to torquesensor 14. A shaft encoder 36 mounted on the wall 24 of the casingmeasures the angular position of the shaft 20.

A computer control means in the form of a micro controller 50 isconnected to the torque sensor 14 and the shaft encoder 36 and receivesinput signals indicative of the torque measured by the torque sensor andthe angular position of the shaft as measured by the shaft encoder. Themicro controller also controls the current applied to the electric brakevia a feedback loop.

When a torque is applied to the shaft 20 to turn the shaft in thedirection A, that torque is measured by the torque sensor 14.

It will be appreciated that the device 10 works by using the brake rotor32 and brake stator coil 28 to provide increasing resistance to theturning of the shaft 20 about its longitudinal axis which is measured bythe torque sensor 14. The resistance can be quickly and accuratelycontrolled by varying the current applied to the brake rotor 32. Thetorque applied to the shaft 20 is measured by the torque sensor 14 andthis therefore gives a measurement of the performance of a patient'sjoint or combination.

The performance of virtually any joint can be measured using a flexiblerope and a capstan fitted to coupling 26 to monitor movement of thejoint. It will be readily appreciated that other mechanisms may befitted to the coupling to convert rotational movement to other types ofmovement for testing other types of movement. It is also envisaged thattwo or three devices could be operated simultaneously in different axesat the same time to test the performance of more complex actions inthree dimensions such as serving a tennis ball, kicking a football orthe like.

However, simply measuring the performance of the joint as describedabove, by measuring the torque a joint may generate will not measuretrue joint performance unless a patient is trying as hard as they cani.e. giving maximal effort. Also simply measuring performance based onapplication of a fixed load does not provide an indication of thesincerity of effort that a patient is applying to the task.

Thus, in order to make it more difficult to misrepresent the trueperformance test by making a sub-maximal effort, in a particularlypreferred embodiment, the computer control means 50 is programmed tovary the resistive load provided by the electric brake, whilst the shaft20 is being turned by the patient. This makes it much more difficult fora patient to misrepresent the test since whilst it is relativelystraightforward to decide to make a “50% effort, say, when movingagainst an unchanging resistance, when the resistance changescontinuously, the patient is unable to accurately and quickly calculatethe changing level of effort they need to apply to be consistent withtheir original level of effort.

The system thus varies the resistive load applied to the electric brake,changing the resistance to turning of the shaft by the patient. Thedevice 10 measures the torque applied to the shaft 20 by the patient andcorrelates the measured torque with the resistance applied to theturning of the shaft 20.

The device 10 rapidly varies the resistance to the turning of the shaft20 during a single exercise performed by the patient. Thus, if thepatient is asked to, say, pull his/her fist up to his shoulder, in thatone movement, the resistance to the turning of the shaft would varyseveral times.

Several patterns of resistance may be applied including sinusoidal, “sawtooth” and non-uniform patterns. The patterns depicted in FIGS. 2 and 3are of a step change nature.

With reference to FIG. 2 for a patient who is making a 100% effort eachtime, the relationship L between the measured torque 52 and theresistance applied 54 is shown to be fairly constant. If however, apatient is attempting to cheat the test by making only a “50% effort”,then they will not be able to maintain that sub-maximal 50% effortconsistently as the load is varied and a greater variation/standarddeviation in the relationship L of the measured torque and the resistiveforce will be measured, as shown in FIG. 3. The tests may also berepeated, with variations in the patient's performance furtherindicating sub-maximal effort.

The variation of the resistive load may be based on position of theshaft as measured by either the encoder or time. The variation may becontinuously varied for example by a ramped load or a stepped load orboth. The variation may be increasing or decreasing or consistentstopping.

The electric brake may be replaced by an equivalent element such as aneddy current coupling or similar controlled coupling device orservomotor. Further, the method of providing a variable resistance couldbe a hydraulic motor or actuator with a variable flow control so thatthe oil flow could be restricted to provide a controlled resistivetorque.

The system may be active or passive. For example, in an active system,the resistive electric brake could be replaced by a variable torqueservo drive.

Because the device provides a repeatable way of measuring jointperformance, it is possible to measure improvement in joint performance,for example, the performance of an elbow could be measured on a weeklybasis and increases in the strength and range of movement of the jointperformance measured and tracked.

It will appreciated by those skilled in the art that many of variouswell known algorithms and statistical techniques can be used forproviding figures correlating the patient's effort to the load orresistance. The particular algorithm used is not critical.

Coefficient of Correlation—Mathematical and or Visual methods

One suitable formula is:$r = \frac{{\Sigma\quad{XY}} - \frac{\Sigma\quad X\quad\Sigma\quad Y}{N}}{\sqrt{\left( {{\Sigma\quad X^{2}} - \frac{\left( {\Sigma\quad X} \right)^{2}}{N}} \right)\left( {{\Sigma\quad Y^{2}} - \frac{\left( {\Sigma\quad Y} \right)^{2}}{N}} \right)}}$Using this algorithm, the correlation coefficient is used to determinethe relationship between two properties, Y and X being values of theforce applied by the patient and the applied resistance, respectively.Another form is:${{Correlation}\quad{Coefficient}} = \frac{{Cov}\left( {X,Y} \right)}{\left. {StdDevX} \right)({StdDevY})}$Where:−1<=Correlation Coefficient<=1And:Cov(X, Y)=1/nΣ(x ^(i) −x)(y ^(i) −y)where y and x are the values of the force applied by the patient and theapplied resistance, respectively.

A correlation coefficient of +1.0 is a strong positive result. As x goesup, y always goes up. A correlation of +0.5 is a weak positive, with ytending to go up as x does. A correlation coefficient of 0 shows nocorrelation, with 0.5 being weak negative and −1.0 being a strongnegative.

A positive number close to 1 indicates a high degree of correlation andstrongly suggests sincerity of effort.

FIG. 4 illustrates a further embodiment of a device for performancetesting of joints. The movable member in this embodiment is a piston 102slideable within a cylinder 104 containing hydraulic fluid. Forces Facting to push the piston into the cylinder cause the pressure in thehydraulic cylinder to increase and the discharge of hydraulic fluidthrough an exit pipe 106. An electrically operable adjustable controlvalve 108 controls the ease of flow through the exit pipe by varying itsdegree of closure. Expelled hydraulic fluid may pass into a reservoir110. A pressure sensor 112 in the hydraulic cylinder measures thepressure therein which depends on the force F applied to the piston. Thesensors measurements are sent to a computer control means 120 which alsocontrols the valve 108. The degree of resistance to movement of thepiston may be varied by the control valve 108. By comparing that withthe measure pressure the correlation between the force applied and theresistance to movement can be calculated by a computer control means 120which controls the degree of opening of the valve and receives and inputfrom the pressure sensor 112 measuring the hydraulic pressure in thecylinder. By varying the resistance to movement of the piston as apatient pushes the piston into the cylinder, the relationship betweenthe applied force and resistance can be measured, to test the patient'ssincerity of effort by determining the variation between the two.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described.

The present embodiments are, therefore, to be considered in all respectsas illustrative and not restrictive.

1. A device for performance testing of a human's joints comprising: amoveable member; a sensor for measuring force applied to the moveablemember by the human; and a resistance means for varying the resistanceto movement of the moveable member at least once during a singlemovement of the moveable member by the human; and means for comparing,or determining the correlation between, the measured force applied tothe movable member with the resistance to movement of the movable memberfor assessing the response of the human to the variation in resistanceto provide an indication of the human's sincerity of effort in movingthe movable member.
 2. The device of claim 1 wherein the moveable membercomprises a shaft.
 3. The device of claim 2 wherein the sensor comprisesa torque sensor for measuring torque applied to the shaft.
 4. The deviceof claim 3 wherein the resistance means comprises a coupling means forvariably coupling the shaft to the torque sensor to thereby vary theresistance to turning of the shaft.
 5. The device of claim 4 wherein theresistance is continuously variable between a state where there is nocoupling between the shaft and the torque sensor and a state in whichthe shaft is fully coupled to the torque sensor.
 6. The device of claim2 wherein the coupling means comprises an electric brake.
 7. The deviceof claim 3 including a control means for receiving input data from thetorque sensor, said input data indicative of the torque applied to theshaft by a user.
 8. The device of claim 7 wherein the control means isalso arranged to provide control signals to the resistance means to varythe resistance applied to the shaft.
 9. The device of claim 7 includingan encoder for measuring the position of the shaft.
 10. The device ofclaim 9 wherein the control means also receives signals indicative ofthe angular position of the shaft from the encoder.
 11. The device ofany one of claims 10 wherein the control means is arranged to determinethe correlation between the resistance to turning the shaft and thetorque measured by the torque sensor
 12. The device of claim 1 whereinthe resistance means is arranged to vary the resistance more than onceduring a single movement.
 13. The device of claim 1 wherein theresistance means is arranged to vary the resistance once during a singlemovement.
 14. The device of claim 12 wherein the resistance means isarranged to vary the resistance in a step change fashion.
 15. A methodof measuring a person's joint performance and simultaneously measuringsincerity of effort by getting the person to apply force to a movablemember to move that member; varying the resistance to movement of themember at least once during a single movement; measuring the forceapplied to the member by the person, recording the resistive forceapplied; and assessing the correlation between the resistive forceapplied and the measured torque to thereby assess the sincerity ofeffort applied by the person to movement of the member.
 16. A method ofsincerity of effort testing of a person's joint performance by measuringthe torque applied to a shaft by one of the person's joints comprisingthe steps of: applying a varying resistive force to turning of theshaft, the resistance to turning of the shaft being varied at least onceduring a single movement; measuring the torque applied to the shaft;recording the resistive force applied; and assessing the correlationbetween the resistive force applied and the measured torque to providean indication of the sincerity of effort applied by the person tomovement of the shaft.